This invention relates generally to safety apparatus and more particularly to a rope grab device for use on a safety line.
Due to the enactment of various safety laws, persons working at elevated positions, e.g., when washing the upper story windows of a building, etc., are required to be protected against falls. One common approach to achieve that end is the use of a safety belt which is worn on the worker's waist or a harness worn on the worker's torso. The belt/harness typically includes a D-ring or some other metal loop fixedly mounted on it. The D-ring is arranged to be connected, via a lanyard, to a "rope grab" device which is mounted on a safety line. The safety line typically comprises a rope, cable or other type of strong line which extends vertically from a fixed elevated anchor point downward past the point at which the worker is located. In fact in many applications the line extends all the way to the ground. The rope grab is arranged to slide along the safety line to follow the worker up or down the structure on which the worker is working. In the event that the worker should fall off of the structure the rapid downward pull on the rope grab caused by the momentum of the worker causes the rope grab to automatically immediately engage and lock itself into a fixed position on the safety line, thereby arresting the worker's fall and supporting him/her until he/she can be rescued.
While prior art rope grabs are effective for preventing falls and hence are generally suitable for their intended purposes their operation to arrest the fall of a worker may render them and/or the safety lines on which they are mounted unsuitable for safe reuse. In this regard once the rope grab has been called upon to arrest the fall of a worker the stresses imparted to it and to the safety line on which it is located may weaken the rope grab and/or the safety line to a point where reuse would be unsafe.
Heretofore, some prior art lanyards for connecting the worker's safety belt or harness to the rope grab or to a fixed anchor point in safety systems have included some means to indicate that the lanyard has been stressed by a fall. For example, in U.S. Pat. No. 4,253,54 (Dalmaso) there is disclosed a lanyard which when stressed by a fall results in the breakage of stitching and the release of a flag to indicate that occurrence. In U.S. Pat. Nos. 2,613,865 (Rose); 3,444,957 (Ervin, Jr.); 3,804,698 (Kinloch); 4,446,944 (Forrest et al.); and 4,538,702 (Wolner) there are disclosed shock absorbing safety belts or lanyards which include looped portions which are extended when the device is stressed, such as occurs when arresting a fall.
In U.S. Pat. No. 4,877,110 (Wolner) there is disclosed a safety device with a retractable lifeline which is reeled up in a housing attached to a harness worn by the worker. The end of the safety line is attached to an elevated fixed anchor point. The device includes a shear pin with a minimum predetermined amount of the lifeline wound around it within the housing so that when the safety device operates to arrest the fall of the worker the shear pin breaks and enable that predetermined amount of safety line to exit the housing. A label is located on that portion of the safety line to indicate that the safety device must be serviced or checked prior to reuse.
Other devices have been described in the patent literature for indicating the existence of stress on a member. For example U.S. Pat. No. 3,025,995 (Koelsch et al) discloses a container or case having deformable corners to indicate the absorption of a shock thereto. U.S. Pat. Nos. 2,294,897 (Ellis); 2,428,559 (Ellis); and 3,801,340 (Ellis) disclose adherent brittle films used on rigid articles which crack at predetermined strain levels to indicate stress on the articles.
Thus, the prior art has not addressed the problem of indicating the operation of a rope grab on a safety line to arrest a worker's fall so that the rope grab and/or safety line can be taken out of use for disgarding or for checking and/or refurbishment.